sure (shr, shûr)
adj. sur·er, sur·est
1. Confident, as of something awaited or expected: I am sure we will win the game.
2. Impossible to doubt or dispute; certain: We have sure proof of his innocence.
a. Bound to come about or happen; inevitable: a sure victory for the team.
b. Having one's course directed; destined or bound: She is sure to succeed.
a. Certain not to miss, slip, or err; steady: a sure grip on the suitcase.
b. Not hesitating or wavering; firm: sure convictions.
a. Worthy of being trusted or depended on; reliable: a sure friend.
b. Free from or marked by freedom from doubt: She is sure of her friends.
6. Careful to do something: Be sure to turn off the stove.
7. Obsolete Free from harm or danger; safe.
for sure Informal
Certainly; unquestionably: We'll win for sure.
To establish something without doubt; make certain: Make sure he writes it down.
As one might have expected; certainly.
to be sure
[Middle English, from Old French, safe, from Latin sēcūrus; see SECURE.]
Synonyms: sure, certain, confident, positive
These adjectives mean feeling or showing no doubt. Sure and certain are frequently used interchangeably; sure, however, is the more subjective term, whereas certain may imply belief based on experience or evidence: "Never teach a child anything of which you are not yourself sure" (John Ruskin). "We went that early because we were certain it was the only way we would ever get a seat" (Ann Patchett).
Confident suggests assurance founded on faith or reliance in oneself or in others: "It goes without saying that a smiling, confident person will do better in an interview than a surly one" (Barbara Ehrenreich).
Positive suggests full, emphatic certainty: "We were young, and I was positive nothing really terrible could happen to us" (Nora Roberts). See Also Synonyms at certain.
The American Heritage® Dictionary of the English Language, Fifth Edition copyright ©2018 by Houghton Mifflin Harcourt Publishing Company. All rights reserved.